<html>
    <head>
        <meta http-equiv="content-type" content="text/html; charset=UTF-8">
        <link rel="stylesheet" href="index.css" />
        <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    </head>
    <body>
        <div id="app-5">
            <p>{{ message }}</p>
            <button v-on:click="reverseMessage">反转消息</button>
        </div>

        <script src="index.js"></script>
    </body>
</html>